I have a parse error using eloquent with slim3

I'm following the codecourse video series Authentication with Slim 3, which is about 3 years old. I've hit a snag when it comes to using eloquent to access a mysql database. (the relevant video: https://www.youtube.com/watch?v=70IkLMkPyPs )

the code wasn't quite the same as that currently recommended on the instructions on illuminate/database's docs, so I've modified the code slightly to follow that standard, but regardless of whether I follow Alex's code oon the vid or the following, a parse error results.

$app = new \Slim\App([
  'settings' => [
    'displayErrorDetails' => true,

    'db' => [
      'driver' => 'mysql',
      'host' => 'localhost',
      'database' => 'opium3',
      'username' => 'root',
      'password' => 'root',
      'charset' => 'utf8',
      'collation' => 'utf8_unicode_ci',
    ]

  ],

]);


$container = $app->getContainer();

/*set up eloquent to use outside laravel*/
use \Illuminate\Database\Capsule\Manager as Capsule;
$capsule = new Capsule;
$capsule->addConnection($container['settings']['db']);
$capsule->setAsGlobal();
$capsule->bootEloquent();

Running the app produced this error:

Parse error: syntax error, unexpected '=' in /var/www/public/opium3/vendor/illuminate/database/DatabaseManager.php on line 65

I'm running this locally on a scotchbox vagrant set up, if that's relevant. There's a similar question at Parse error when run illuminate/database/capsule with bootEloquent() in PHP

but this answer doesn't resolve my issue, since the server is running php7. I have also tried installing packages recommended by illuminate/database, installing php-mbstring, and editing the php.ini file, on the server, but the error persists.

Am I missing something obvious?